Synchronization of joint transmissions with multiple access points

Abstract

A first access point (AP) generates and transmits a first physical layer (PHY) data unit for initiating a joint channel sounding procedure between a group of APs, including the first AP and one or more second APs, and one or more client stations. The first PHY data unit is generated to indicate that the first PHY data unit is of joint channel sounding type. The first AP generates and transmits a second PHY data unit for initiating synchronous data transmissions by the group of APs. The second PHY data unit is generated to indicate that the second PHY data unit is of a joint data transmission type. The synchronous data transmissions initiated by the second PHY data unit are steered using beamforming parameters determined based on the joint sounding procedure. A synchronous data transmission by a second AP is adjusted based on the relative timing offset.

What is claimed is: 
     
       1. A method for wireless communication by a first access point (AP) in joint communications involving multiple APs, the method comprising:
 generating, at the first AP, a first physical layer (PHY) data unit for initiating a joint channel sounding procedure between i) a group of APs including the first AP and one or more second APs and ii) one or more client stations, including generating the first PHY data unit to include in a first PHY preamble of the first PHY data unit a) a first training signal, and b) an indication that the first training signal is to be used by each of one or more second APs for determining a relative timing offset between the first AP and the second AP in connection with synchronous data transmissions by the group of APs; 
 transmitting, by the first AP, the first PHY data unit to the one or more second APs to initiate the joint sounding procedure; 
 generating, at the first AP, a second PHY data unit for initiating synchronous data transmissions by the group of APs to the one or more client stations, including generating the second PHY data unit to include in a second PHY preamble of the second PHY data unit i) a second training signal, and ii) an indication that each of the one or more second APs is to determine the relative timing offset between the first AP and the second AP using a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit; and 
 transmitting, by the first AP, the second PHY data unit to the one or more second APs to initiate synchronous data transmissions by the group of APs to the one or more client stations, wherein i) the synchronous data transmissions are steered to the one or more client stations using beamforming parameters determined based on the joint sounding procedure and ii) a synchronous data transmission by a second AP among the one or more second APs is adjusted based on the relative timing offset determined based on a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit. 
 
     
     
       2. The method of  claim 1 , wherein
 generating the first PHY data unit incudes generating the first PHY data unit to further include an identifier corresponding to the first AP, and 
 generating the second PHY data unit incudes generating the second PHY data unit to further include the identifier corresponding to the first AP. 
 
     
     
       3. The method of  claim 2 , wherein generating the first PHY data unit to include an identifier corresponding to the first AP comprises generating the first PHY data unit to include one or more of i) one or more bits of a basic service set (BSS) color associated with the first AP, ii) a master AP identifier associated with the first AP and iii) a joint group identifier associated with the group of APs including the first AP and the one or more second APs. 
     
     
       4. The method of  claim 1 , wherein generating the second PHY data unit to include the indication that each of the one or more second APs is to determine the relative timing offset between the first AP and the second AP using a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit comprises rotating modulation of a field of the second PHY preamble of the second PHY data unit to indicate that each of the one or more second APs is to determine the relative timing offset between the first AP and the second AP using a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit. 
     
     
       5. The method of  claim 1 , wherein generating the second PHY data unit comprises generating the second PHY data unit to include a padding field to provide the one or more second APs sufficient time to adjust the relative timing offset prior to the synchronous data transmissions by the group of APs, wherein the synchronous data transmissions by the group of APs are to be initiated a predetermined time interval after an end of the second PHY data unit. 
     
     
       6. The method of  claim 5 , wherein generating the second PHY data unit comprises generating the second PHY data unit to further include, in the second PHY preamble of the second PHY data unit, an indication of a duration of the padding field. 
     
     
       7. The method of  claim 1 , wherein generating the second PHY data unit comprises generating the second PHY data unit to include one or both of i) midamble or ii) postamble to provide the one or more second APs sufficient time to adjust the relative timing offset prior to the synchronous data transmissions by the group of APs, wherein the synchronous data transmissions by the group of APs are to be initiated a predetermined time interval after an end of the second PHY data unit. 
     
     
       8. The method of  claim 1 , wherein generating the second PHY data unit comprises generating the second PHY data unit to include one or both of midamble and postamble to provide the one or more second APs sufficient time to adjust the relative timing offset prior to the synchronous data transmissions by the group of APs, wherein the synchronous data transmissions by the group of APs are to be initiated a predetermined time interval after an end of the second PHY data unit. 
     
     
       9. The method of  claim 8 , wherein generating the second PHY data unit comprises including one or more training fields in the one or both of midamble and postamble. 
     
     
       10. A first access point (AP) comprising:
 a wireless network interface device comprising one or more integrated circuit (IC) devices configured to:
 generate a first physical layer (PHY) data unit that for initiating a joint channel sounding procedure between i) a group of APs including the first AP and one or more second APs and ii) one or more client stations, the one or more IC devices being configured to generate the first PHY data unit to include in a first PHY preamble of the first PHY data unit a) a first training signal, and b) an indication that the first training signal is to be used by each of one or more second APs for determining a relative timing offset between the first AP and the second AP in connection with synchronous data transmissions by the group of APs, 
 
 control the wireless network interface device to transmit the first PHY data unit to the one or more second APs to initiate the joint sounding procedure, 
 generate a second PHY data unit for initiating synchronous data transmissions by the group of APs to the one or more client stations, the one or more IC devices being configured to generate the second PHY data unit to include in a second PHY preamble of the second PHY data unit i) a second training signal, and ii) an indication that each of the one or more second APs is to determine the relative timing offset between the first AP and the second AP using a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit, and 
 control the wireless network interface device to transmit the second PHY data unit to the one or more second APs to initiate synchronous data transmissions by the group of APs to the one or more client stations, wherein i) the synchronous data transmissions are steered to the one or more client stations using beamforming parameters determined based on the joint sounding procedure and ii) a synchronous data transmission by a second AP among the one or more second APs is adjusted based on the relative timing offset determined based on a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit. 
 
     
     
       11. The first AP of  claim 10 , wherein the one or more IC devices are further configured to
 generate the first PHY data unit to further include an identifier corresponding to the first AP, and 
 generate the second PHY data unit to further include the identifier corresponding to the first AP. 
 
     
     
       12. The first AP of  claim 11 , wherein the one or more IC devices are configured to generate the first PHY data unit to include one or more of i) one or more bits of a basic service set (BSS) color associated with the first AP, ii) an identifier of associated with the first AP and iii) a joint group identifier associated with the group of APs including the first AP and the one or more second APs. 
     
     
       13. The first AP of  claim 10 , wherein the one or more IC devices are configured to generate the second PHY data unit to include the indication that each of the one or more second APs is to determine the relative timing offset between the first AP and the second AP using a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit at least by rotating modulation of a field of the second PHY preamble of the second PHY data unit to indicate that each of the one or more second APs is to determine the relative timing offset between the first AP and the second AP using a) the first training signal in the first PHY preamble of the first PHY data unit and b) the second training signal in the second PHY preamble of the second PHY data unit. 
     
     
       14. The first AP of  claim 10 , wherein the one or more IC devices are configured to generate the second PHY data unit to include a padding field to provide the one or more second APs sufficient time to adjust the relative timing offset prior to the synchronous data transmissions by the group of APs, wherein the synchronous data transmissions by the group of APs are to be initiated a predetermined time interval after an end of the second PHY data unit. 
     
     
       15. The first AP of  claim 14 , wherein the one or more IC devices are configured to generate the second PHY data unit to further include, in the second PHY preamble of the second PHY data unit, an indication of a duration of the padding field. 
     
     
       16. The first AP of  claim 10 , wherein the one or more IC devices are configured to generate the second PHY data unit to include one or both of i) midamble or ii) postamble to provide the one or more second APs sufficient time to adjust the relative timing offset prior to the synchronous data transmissions by the group of APs, wherein the synchronous data transmissions by the group of APs are to be initiated a predetermined time interval after an end of the second PHY data unit. 
     
     
       17. The first AP of  claim 10 , wherein the one or more IC devices are configured to generate the second PHY data unit to include one or both of midamble and postamble to provide the one or more second APs sufficient time to adjust the relative timing offset prior to the synchronous data transmissions by the group of APs, wherein the synchronous data transmissions by the group of APs are to be initiated a predetermined time interval after an end of the second PHY data unit. 
     
     
       18. The first AP of  claim 17 , wherein the one or more IC devices are configured to generate the second PHY data unit to include one or more training fields in the one or both of midamble and postamble.